If you get maternity allowance then you could check if you might be eligible for universal credit as well. I got it when my mat pay went down to SMP and then unpaid. You can use this calculator to see if you might be eligible. https://www.entitledto.co.uk/
I got made redundant week before I found out I was pregnant so am just staying off. When I filled the gov form in they do ask if you are self employed, helping your partners business or any other income so I don’t think you can claim then get a job
I believe you can do private work but not for your employer you are claiming MA from?